1. Field of the Invention
It is important to stretch fibers resolved from a sliver and to orient and maintain the stretched fibers in parallelized condition as they are transported from a resolving device to a fiber collection surface of a spinning rotor. The most effective means of transporting such fibers utilized heretofore has been by an accelerated air stream passing through a fiber feed tube extending from the resolving device to the fiber-collection surface. However, intermolecular friction and friction between the air and the walls of the feed channel through which the air flows create shear stress in the air stream which results in turbulence. Consequently, fibers are frequently improperly and randomly oriented when they reach the spinning rotor, so that the quality and consistency of yarn spun in the rotor has suffered.
On the other hand, in the region in which the air stream contacts the rigid walls of a feed tube, the molecular random or mixing motion is damped by friction with the tube walls so that a boundary layer of laminar flow results. However, at locations spaced from the tube walls, the damping effect of the wall decreases and the internal friction of the air molecules again creates conditions such that turbulence is predominant. Again, fibers carried by the air stream are effected by such turbulence so that they cannot be maintained in a desired consistently oriented, generally parallel condition.
2. Prior Art
A variety of feed tubes for transporting fibers from one location to another are known. The following prior art is the most relevant to the present invention. The prior art disclosures do not recognize or solve the turbulence problems overcome by the present invention; and feed tubes constructed in accordance with those disclosures do produce turbulent airflow conditions, or are not suitable for parallelizing fibers, or otherwise are incapable of orienting fibers satisfactorily to cooperate with an open-end spinning machine for forming yarn of consistent quality and desired characteristics.
Prior apparatus for accelerating an air current for transporting fiber is disclosed in DT-AS 1,510,741 which includes a frustoconical or otherwise reduced cross-sectional area feed tube. While the fibers being transported to the spinning rotor may be oriented as desired initially, the aforesaid conditions of turbulence prevail and prevent controlled orientation of the fibers at the point of deposit on the fiber collection surface of a spinning rotor.
Prior feed tubes having a conic portion followed by a cylindrical portion have been proposed. One such feed tube arrangement is disclosed in DT-OS 1,922,743. In this case, the conic portion functions as a condenser. The cylindrical portion merely forms a passage through the spinning rotor housing cover and cooperates with the conic portion to hold the cover firmly in place. Another feed tube is shown in DT-OS 1,925,999, but the degree of conicity of the conic portion is too slight to impart sufficient acceleration to the fibers for effecting a consistent fiber lay. The fibers are accelerated by an auxiliary vacuum air current which acts on the fibers in the region between the conic and cylindrical portion. The effect of this sudden air current is to create substantial turbulence whereby the lay of the fibers is undesirably disturbed.
Another variation in feed tubes is disclosed in U.S. Pat. No. 3,521,440 in which the cross-sectional shape of a tube is varied along its length without changing the cross-sectional area of the tube. This type of tube serves the function of urging fibers together to form a concentrated fiber stream and is used for fibers delivered by a drafting system rolling mill. In this apparatus, there is no acceleration of the air which accompanies the fiber stream.